Adduct Thermosetting Surfacing Film and Method of Forming the Same

ABSTRACT

In various embodiments, the invention provides an in-situ adduct formed by reacting liquid, solid, and/or semi-solid epoxy resins with a di-carboxylic acid functionalized polymer. The adducting process at least doubles the viscosity of the mixture. A hot melt thermosetting surfacing film and composite formed using the adduct are also disclosed. Methods of preparing and using are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationNo. 61/409,692, filed on Nov. 3, 2010, the disclosure of which isincorporated herein in its entirety for all purposes.

BACKGROUND OF THE INVENTION Field of the Invention

This invention relates, in general, to an adduct of one or more resinsand a functionalized polymer and in various aspects to a hot meltthermosetting surfacing film and methods for their preparation and use.

Description of Background Art

Conventional painting processes for cured composite parts requireundesirable, repeated sand-fill-sand steps to prepare the surface beforeapplying the paint primer. The process is time-consuming and leads tohigh labor costs. A surfacing film, which applied at the time of layupand molding of the composite part, provides a ready-to-prime, smooth,and porosity or pinhole-free protecting surface (either with light scuffsanding or without sanding) for a composite laminate can significantlysimplify the surface preparation for painting.

High viscosity and controlled flow are generally important for preparinga good surfacing film. Currently, mainly two approaches are used toincrease the viscosity and reduce the flow of the film. One is by usinghigh molecular weight raw materials, such as high molecular weight resinor rubber (e.g., high molecular weight/high melting point solid epoxyresin). The other approach calls for adding various fillers with highfiller loadings. High filler loading contributes to good sandingproperties of the cured film and low print-through or readout of theunderlying fiber, honeycomb core, woven laminate or other surfacepattern. However, existing techniques for increasing viscosity also havesignificant negative impact on the resin mixing and film coatingprocesses. For example, it is difficult to make light-weight or thinfilm with a high viscosity resin especially in a hot melt process.

One of the concerns arising when using high molecular weight materialsor high loading of fillers to raise the viscosity of the resin is thatthe resulting film might be too dry. The material likely will not haveideal tack at room temperature, thus making layup difficult if the filmwill not adhere to other layers during the layup process. Furthermore,such a material will have inadequate drapability. Both of these featuresmake the material less desirable from a processability standpoint. Forsome commercial products it is difficult or nearly impossible to processsuch high molecular weight materials using the hot melt method due toultra high viscosity of these materials. To overcome these difficulties,a solvent process, therefore, must be used.

Besides inducing high viscosity that causes poor processability, highfiller loading also negatively affects mixing of and coating with theresin. High molecular weight and high filler loading also tend to havesignificant negative impact on the cured film physical properties, e.g.,toughness and adhesion strength.

Currently there are two primary methods to make films: (1) a solventprocess, and (2) a hot melt process. In a solvent process,processability is less of a problem with high viscosity systems, eitherdue to high molecular weight material and/or high filler loadingsbecause more or less solvent can be added to the system to adjust theviscosity to achieve good mixing of ingredients and allow goodimpregnation of the substrate with the solvated resin. In many cases,however, a hot melt process is preferred over the solvent process due tothe material costs and environmental concerns associated with using avolatile solvent. Since the residual solvent is volatile, it can causeproblems such as porosity/fish eye (craters), orange peel, sag, and thelike. Attempts to remove residual solvent by application of highertemperatures or longer heating times can lead to over drying andnegatively affect film properties such as tack and drape. In addition, asolvent process-derived product tends to have residual solvent(s) in theproduct, which can outgas during cure and form cosmetic defectsrequiring additional rework/repair. On the contrary, a hot melt processrequires the resin components to have a relatively low viscosity. It isdifficult to adjust the raw input materials for easier hot meltprocessing while still achieving a resulting product with desirableperformance.

In light of the foregoing, it would be beneficial to have resincompositions and methods of using these compositions which overcome theabove and other disadvantages, producing films with desirableproperties.

BRIEF SUMMARY OF THE INVENTION

In various embodiments the invention provides an adduct and athermosetting surfacing film formed from this adduct. In an exemplaryembodiment, the adduct is formed by the mixing or reaction of a resinwith a polymer. In an exemplary embodiment, the resin is an epoxy resin.In various embodiments, the polymer is a carboxylic acid functionalizedpolymer. In an exemplary embodiment, the adduct is formed by reacting anepoxy resin with a carboxylic acid polymer. In various embodiments, thesurfacing film is configured for use in a hot melt process. An exemplaryadduct is a hot melt thermosetting surfacing composition. The surfacingfilm can be used in various composite material applications including,but not limited to, vacuum bag molding, pressure bag molding, autoclavemolding, hydraulic press molding, resin transfer molding (RTM),infusion/injection molding, and the like.

In various embodiments, the invention provides a hot melt thermosettingsurfacing film composition including an adduct formed by reacting one ormore liquid, solid, and/or semi-solid epoxy resins with a carboxylicacid functionalized polymer. In various embodiments, the carboxylic acidfunctionalized polymer includes with one or more carboxylic acidfunctional groups per molecule. In various embodiments, at least about50%, 60%, 70%, 80%, 90% or about 100% of the monomeric units in thepolymer include at least one carboxylic acid moiety. In an exemplaryembodiment, the adducting process increases the viscosity of the resin,e.g., at least about two-fold. In various embodiments, the adduct isformed in-situ before adding other resins, fillers, a curing agent, anda catalyst to form the final formulation.

Various aspects of the invention relate to a thermosetting surfacingfilm composition made from a reactant mixture of cross-linkable resins,the mixture including: (A) from about 5% to about 60% (by weight of thetotal resin composition) of a liquid, semi-solid, or mixture of an epoxyresin comprising at least one low viscosity liquid epoxy resin, (B) fromabout 2% to about 40% (by weight of the total resin composition) of oneor more solid bis-phenol A based epoxy resins having a softening pointrange from about 50° C. to about 130° C., (C) from about 1% to about 30%(by weight of the total resin composition) of solid epoxy phenolnovolac, epoxy cresol novolac or other multifunctional epoxy having afunctionality of about 2.2 or more, (D) from about 1% to about 20% (byweight of the total resin composition) of a functionalized polymer, (E)optionally from about 0.001% to about 5% (by weight of the total resincomposition) of a defoamer and/or air release agent, (F) from about 20%to about 60% (by weight of the total resin composition), with or withoutan organic surface treatment, of a filler material comprising one ormore (e.g., one, two or three) fillers and/or pigments, the fillermaterial including: (i) a member selected from silica, alumina, aluminumhydroxide, magnesium oxide, zinc borate, zinc-magnesium complex,ceramics, high melting thermoplastic polymer powders, zinc stannatebased compounds, antimonite trioxide, carbon black, titanium dioxide,ground glass, milled or chopped fiber, glass spheres, hollow glassbeads, whiskers, minerals, calcium carbonate or a combination thereof.

In an exemplary embodiment, the thermosetting surfacing film of theinvention has an average particle size from about 5 nm to about 100microns, (G) from about 2% to about 30%, e.g., about 10% (by weight ofthe total resin composition) of a curing agent (e.g., dicy,3,3′-diaminodiphenyl sulfone (3,3′-DDS) , 4,4′-diaminodiphenyl sulfone(4,4′-DDS), 3,4′-diaminodiphenolmethane (3,4′-DDM), or3,4′-diaminodiphenolmethane (3,4′-DDM), (H) from about 0.5% to about 5%(by weight of the total resin composition) of a hardener such as phenolfunctional hardeners, Dicy, an amine, Lewis Acid hardeners and the like,and (I) an optional accelerator or catalyst, e.g., one or more selectedfrom urea, substituted urea, imidazole, substituted imidazole, amine(e.g., primary, secondary, or tertiary substituted or unsubstitutedamine).

In some applications, flame retardancy is desired or required for asurfacing film. In an exemplary embodiment, the invention provides aflame retardant surfacing film. In various embodiments, the film is madeby including a flame retardant agent in the adduct forming the film. Inan exemplary embodiment, a flame retardant surfacing film is prepared bypartially or fully replacing one or more of the liquid, semi solid orsolid epoxy resins with a flame retardant agent and in combination withsome of the filler materials substituted with flame retardant fillers.In an exemplary embodiment, the flame retardant agent is a memberselected from bromine or phosphorous containing aromatic epoxies,high-nitrogen, low-hydrogen containing polymers such as benzoxazines,another inorganic or organic flame retardants while fillers can be amember selected from a number of FR additives, smoke suppressors andchar formers. Exemplary inorganic flame retardants of use in the filmsof the invention include, but are not limited to, aluminum hydroxide orother hydrated mineral compounds, e.g., magnesium hydroxide, magnesiumoxide, zinc borate, borates, phosphate esters, antimony compounds,phosphorous containing reactive flame retardant, or a combinationthereof. In exemplary embodiments, the inorganic solid powders, e.g.,aluminum hydroxide act as both flame retardant and filler.

In various embodiments, the desirable properties of the film areachieved or augmented by the addition to the adduct of one or moremembers selected from smoke suppressants and char formers, such asantimony oxide and zinc borate

In some applications, such as rapid cure, large composite partsmanufacturing, fast cure is required for high productivity requirement,where typical composite cure methods may not be acceptable due to cycletime. For use in such applications, in various embodiments, thisinvention provides fast cure surfacing film. In an exemplary embodiment,the invention provides a fast cure surfacing film can be achieved byselecting different curing agent from the class of compounds, though notlimited to, phenolic compounds, Dicy, DDS and the like, and catalyst,from the class of compounds, though not limited to imidazoles, amines,and substituted/modified amines and the like. By adjusting theconcentration of the curing agent and catalyst in the formulationwithout sacrificing cured surface quality/cosmetics, the composition isamenable to all methods of composite cure, including rapid cycle timesto reduce part production cost through higher throughput rates.

Various aspects of the invention relate to an adduct formed by reactingliquid, solid, and/or semi-solid epoxy resins with a di-carboxylic acidfunctionalized polymer. In various embodiments, the resulting adduct ismixed with one or more of a filler, a pigment, a defoamer, a curingagent, and a catalyst. In various embodiments, the reactant mixture iscured to form a thermosetting film.

The compositions and methods of the present invention(s) have otherfeatures and advantages which will be apparent from or are set forth inmore detail in the following Detailed Description of the Invention,which serves to explain the principles of the present invention(s) byway of presenting certain exemplary embodiments, which are not to beconstrued as limiting

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to various embodiments of theinvention. While the invention will be described in conjunction withthese various embodiments, it will be understood that they are notintended to limit the invention to those embodiments. On the contrary,the invention encompasses alternatives, modifications and equivalents,which may be included within the spirit and scope of the invention asdefined by the appended claims.

For convenience in explanation and accurate definition in the appendedclaims, the terms “up” or “upper”, “down” or “lower”, “top” and“bottom”, “inside” and “outside”, and “upstream” and “downstream” areused to describe features of the present invention with reference to thepositions of such features as displayed in the figures.

In various embodiments, the invention provides a composition or reactantmixture for a thermosetting surfacing film. In various aspects, thesurfacing film is configured for use in a hot melt process. Thesurfacing film can be used in various composite material applicationsincluding, but not limited to, vacuum bag molding, pressure bag molding,autoclave molding, hydraulic press molding, resin transfer molding(RTM), infusion/injection molding, and the like.

In various embodiments, the composition of the invention relates to ahot melt thermosetting surfacing film formed from an adduct prepared byreacting liquid, solid, and/or semi-solid epoxy resins with a carboxylicacid functionalized polymer. The exemplary adducting process increases,e.g., approximately doubles the viscosity of the mixture. In variousembodiments, the adduct is formed in-situ. In various embodiments, thecarboxylic acid functionalized polymer is a di-carboxylic acidfunctionalized polymer. In various embodiments, the functionalizedpolymer is reactive with at least one of the epoxy resins.

Exemplary compositions of the invention include one or more carboxylicacid polymer with a functionality of at least about 2 carboxylic acid(or carboxylic acid derived) moieties per molecule. Exemplaryfunctionalized polymers include conventional diene and olefin polymershaving, or modified to include, from about 0.1 to about 5 wt %,preferably from about 0.5 to about 3 wt % carboxyl, carboxamide,anhydride, epoxy, or amine functionality. In exemplary embodiments,particular functional groups should be capable of reacting with at leastone of the resin system monomers. Representative of such diene polymersare the variety of well known rigid possibly cross-linked copolymers ofbutadiene or isoprene including for example the diene-acrylonitrilecopolymers widely available as nitrile rubbers, copolymers of vinylaromatic monomers and diene monomers such as the styrene-butadienecopolymers known as SBR rubbers, and terpolymers of dienes withacrylonitrile and styrene or vinyl toluene, all of which, when modifiedwith the desired level of functionality, may be described asfunctionalized diene rubbers. Many such rubbers having T_(g) valuesbelow 10° C. and the desired functionality are readily available fromcommercial sources. Also useful are rubbery copolymers of acrylateesters with carboxyl functionality, which may be described ascarboxylated acrylic rubbers. Acrylic polymers with the desired level ofcarboxylic functionality and having T_(g) values in the range of about−25° C. to about 10° C. are also commercially available in a variety offorms. Other polymers which may be similarly modified to includecarboxyl or other functionality include rubber-like copolymers andparticularly graft copolymers of styrene, vinyltoluene or the like andoptionally one or more additional copolymerizable vinyl monomers on arubbery polymeric substrate, using a sufficiently high level, preferablygreater than 60 wt %, of the rubbery substrate component. Specificexamples include rubbery acrylonitrile-butadiene-styrene (ABS) polymers,methylmethacrylate-butadiene-acrylonitrile-styrene (MABS) polymers andthe like.

Modification of polymers to include carboxyl functionality may beaccomplished by a variety of well known processes, includingcopolymerizing monomers with a suitable copolymerizable carboxylicmonomer or by grafting the preformed polymer in solution, suspension, orlatex form, with carboxylic compounds such as maleic anhydride,maleimide, acrylic acid, itaconic acid or the like. Other methods forproviding carboxylated polymers having the necessary character includegrafting the polymers in particle form with mixtures of a monomer and acopolymerizable carboxylic or other functional unsaturated compound toprovide particles having a relatively rigid outer shell with reactivecarboxylic or other functionality, and many such core-shell particulatemodifiers are also known and commercially available. Also suitable arepost reaction processes for functionalizing diene copolymers, olefinsand the like, as recently described in U.S. Pat. Nos. 4,740,552 and4,654,405.

Exemplary base resin systems useful in the subject invention compriseepoxy resins. Epoxy resins are well known to those skilled in the art,and require no further description. The functionality of such resins aregenerally two or higher, and preferred epoxy resins are the glycidylderivatives of bisphenol A, bisphenol F, phenolated dicyclopentadieneoligomers, aminophenols, tri- and tetraphenylolalkanes, andmethylenedianiline. The epoxy resins are generally used with a curingagent which may be, for example, a phenol, dicyandiamide, anhydride oran aromatic amine, e.g., 3,3′- and 4,4′-diaminodiphenyl-sulfone.Catalysts may be used to accelerate the curing reaction, and othercomonomers, thermoplastics both dissolved and dispersed, and otheradditives, for example those required for flow control, may be added.

Various aspects of the invention relate to a reactant mixture, alsoreferred to as a “mixed resin composition” or “resin composition”, forforming a thermosetting surfacing film. The mixed resin compositiongenerally refers to a reactant mixture before being applied to thereinforcing web as a film product. In various respects, the resincomposition includes an adduct, formed by reacting epoxy resin or resinsand a functionalized polymer, and various optional fillers, additives,and the like. Various aspects of the invention relate to a resultingsurfacing film composition for use in composite applications. In someaspects, the term “composition” refers to the resin composition and theresulting film somewhat interchangeably.

In various embodiments, the resin composition is formed fromcross-linkable resins. The resin composition includes liquid,semi-solid, or solid of an epoxy resins combined with a functionalizedpolymer. In various embodiments, the epoxy resins include at least onelow viscosity liquid epoxy resin, one or more solid bis-phenol A basedepoxy resins, and a solid epoxy phenol novolac, epoxy cresol novolac, orother multifunctional epoxy. “Multifunctional epoxy” is to be understoodas used in the materials art and in various aspects means a materialwith a functionality greater than 2 or of a sufficient amount toincrease crosslink density and T_(g) performance. “Functionality” asused in this context refers to the number of epoxide moieties present onthe molecule.

In various embodiments, the resin composition further includes adefoamer and/or air release agent, a filler material, a curing agent,and optionally an accelerator or catalyst. In various embodiments, thefiller material includes one or more inorganic fillers and/or pigments.

The resin composition may include the contents described herein invarious combinations. The resin composition may include from about 1% toabout 20% (by weight of the total resin composition) of a carboxylicacid functionalized polymer. The resin composition may include fromabout 5% to about 60% (by weight of the total resin composition) of anepoxy resin including at least one low viscosity liquid epoxy resin. Theresin composition may include from about 2% to about 40% (by weight ofthe total resin composition) of one or more solid bis-phenol A basedepoxy resin. In various embodiments, the solid bis-phenol A based epoxyresin has a softening point range from about 50° C. to about 130° C. Theresin composition may include from about 1% to about 30% (by weight ofthe total resin composition) of solid epoxy phenol novolac, epoxy cresolnovolac, or other multifunctional epoxy. In various embodiments, thenovolac or multifunctional material has a functionality selected fromabout 4.5 or more, about 3 or more, and about 2 or more. In variousembodiments, the novolac or multifunctional material has a functionalityof about 2.2 or more.

In various embodiments, the resin composition includes a total amount ofthe above liquid epoxies, solid epoxies, carboxylic acid functionalizedpolymer adduct in the range from about 19.5% to about 89.5% (by weightof the total resin composition). In an exemplary embodiment, the resincomposition includes from about 0.001% to about 5% (by weight of thetotal resin composition) of a defoamer and/or air release agent. Invarious embodiments, the resin composition includes from about 10%,about 20%, about 30%, about 40%, about 50%, about 60%, about 70% toabout 80% (by weight of the total resin composition), with or without anorganic surface treatment, of a filler material optionally includingone, two, three, or more fillers and/or pigments. In variousembodiments, the resin composition includes from about 2% to about 10%(by weight of the total resin composition) of a curing agent. Exemplaryresin compositions include from about 0.5% to about 1%, to about 1.5%,to about 2%, to about 2.5%, to about 3%, to about 3.5%, to about 4%, toabout 4.5% to about 5% or more (by weight of the total resincomposition) of an accelerator or catalyst.

In various embodiments, the mixed resin component has a relativelymedium or relatively low viscosity that makes it easy to mix and coatthe thin film with precise thickness control. According to theseembodiments, the composition prior to curing has a viscosity betweenabout 20 Pa·s and about 200 Pa·s, e.g., between about 30 Pa·s to about180 Pa·s, e.g., from about 40 Pa·s to about 160 Pa·s, e.g., from about60 Pa·s to about 140 Pa·s, e.g., from about 80 Pa·s to about 120 Pa·s,In an exemplary embodiment, the viscocity of the resin is at least about20, at least about 40, at least about 60, at least about 80, at leastabout 100, at least about 120, at least about 140, at least about 160,at least about 180 or at least about 200 Pa·s. In various embodiments,the viscocity of the resin is less than about 200, less than about 180,less than about 160, less than about 140, less than about 120, less thanabout 100, less than about 80, less than about 60, less than about 40 orless than about 20 Pa·s.

In various embodiments, the epoxy resin component is a blend of epoxyresins selected to provide tack, viscosity, Tg after cure, and/ortoughness. One will understand from the description herein that avariety of resins may be blended to achieve different processingadvantages and/or field performance.

In various embodiments, the resin component includes a solid epoxyphenol novolac and/or epoxy cresol novolac and/or other multifunctionalresins having an average functionality of about 1.4, 1.6. 1.8, 2.0 or2.2 or more. “Average functionality” is to be understood as used in thematerials and composites industries and generally refers to the numberof reactive functional groups, e.g., epoxides, per molecule for theindividual resin ingredient additive prior to adding it to the mixedresin composition. For example, one molecule may have one functionalgroup whereas another molecule has two functional groups so the “averagefunctionality” is 1.5. Moreover, one will appreciate that the actualaverage functionality may differ from the theoretical number. Forexample, some oligomerization or polymerization may occur duringformation of the resin ingredient or mixture (dimers, trimers,tetramers, etc.) as homopolymerization or copolymerization of anyingredients.

The epoxy resins of use in the invention have good stability at roomtemperature, which provides better handling and process flexibility. Inpart, this allows the resins to be exposed to ambient conditions for anextended time before cure without deterioration of the performance ofthe final product.

Suitable thermosetting resins include, but are not limited to, monomers,oligomers, and/or polymeric materials, which contain at least one ormore reactive functional group in each molecule. Suitable thermosettingresin materials can include, but are not limited to, mixtures or hybridsof epoxy resin, phenolic formaldehyde resins, urea formaldehyde resin,acrylic resin (acrylate), polyester resin (unsaturated), vinyl esterresin, cyanate ester resin, melamine resin, benzoxazine resin,bismaleimide resin, Bismaleimide Triazine (BT) Resin and polyimideresin. Thermoplastic additives may also be added to enhance toughnessproperties. Similarly, combinations or substitutions of flame retardantfillers or FR resin additives may be used or changed to enhance flameretardance properties for different end-use or application requirements.

Suitable low viscosity liquid epoxy resins include, but are not limitedto, bis-phenol A type epoxy resins, bis-phenol F type epoxy resins, andblends of the same. Suitable bis-phenol A epoxy resins include, but arenot limited to liquid, solid, and semi-solid bis-phenol A epoxy resin.

Suitable liquid bis-phenol A type epoxy resins include, but are notlimited to those sold by Dow Chemical Company, Momentive PerformanceMaterials, Inc. (formerly Hexion Specialty Chemicals, Inc.), HuntsmanInternational LLC, and Emerald Performance Materials LLC. Suitable solidbis-phenol A type epoxy resins include, but are not limited to, thosesold by Dow Chemical Company, Momentive Performance Materials, Inc.(formerly Hexion Specialty Chemicals, Inc.), Huntsman International LLC,and Emerald Performance Materials LLC. Suitable bis-phenol F type epoxyresins include, but are not limited to those sold by Dow ChemicalCompany (e.g., bis-phenol F type), Momentive Performance Materials, Inc.(formerly Hexion Specialty Chemicals, Inc.), Huntsman International LLC,and Emerald Performance Materials LLC. Suitable blends include, but arenot limited to, blends of bis-phenol A type and bis-phenol F type epoxysuch as those sold by, but not limited to Dow Chemical Company, HuntsmanInternational LLC, and Emerald Performance Materials LLC.

Suitable multifunctional epoxies include, but are not limited to,semi-solid multifunctional epoxies. Suitable semi-solid multifunctionalepoxies include, but are not limited to, multifunctional phenol novolacepoxy resin, bis-phenol A type novolac epoxy resin, bis-phenol F typenovolac epoxy resin, tetrafunctional epoxy resin, and cresol novolacepoxy resin such as those sold by companies such as Dow ChemicalCompany, Momentive Performance Materials, Inc. (formerly HexionSpecialty Chemicals, Inc.), Huntsman International LLC, and EmeraldPerformance Materials LLC. Other multifunctional epoxy resin materialsmay be used such as trifunctional and tetrafunctional epoxy resin suchas those sold by Momentive Performance Materials, Inc. (formerly HexionSpecialty Chemicals, Inc.), Huntsman International LLC, and EmeraldPerformance Materials LLC

In various embodiments, a reactant for making the adduct is afunctionalized polymer. In various embodiments, the polymer is acarboxy-containing polymer. In an exemplary embodiment, thefunctionalized polymer is carboxyl terminated copolymer of butadiene andacetonitrile such as those sold by Emerald Performance Materials LLC,Hexion Specialty Chemicals and Huntsman International LLC. The inventioncan be practiced by the addition of a pre-formed functionalized polymerto an epoxy resin in situ or by use of a preformed intermediate thatincludes both the functionalized polymer and the epoxy resin.

One will appreciate that a variety of curing agents (either hardeneralone, or hardener in conjunction with a catalyst system) may be used.Suitable curing agents (hardeners or hardeners in conjunction withsuitable catalyst(s)) can include, but are not limited to,Dicyandiamide, polyamines, e.g., 3,3′-DDS or 4,4′-DDS, various modifiedaliphatic and cycloaliphatic amines or adducts, imidazole, substitutedimidazole or encapsulated imidazole. In an exemplary embodiment, theresin composition includes dicyandiamide. Dicyandiamide (“dicy”) is apopular hardener for epoxies, e.g., for 250° F. cure epoxy systems. Ithas 4-5 functional amino groups in a cyano structure (NH₂C(NH)(NHCN)),and is a precursor to the melamine resin group (CAS 461-58-5).

Suitable catalysts include, but are not limited to, urea and modifiedurea such as those sold by Air Products and Chemicals, Inc., DowChemical Company, Emerald Performance Materials LLC, AlzChem TrostbergGmbH, and AC Catalysts Inc. and imidazoles and modified imidazoles suchas those sold by Air Products and Chemicals, Inc. and AC Catalysts Inc.The curing agents may be pre-dispersed in liquid epoxy resin. In variousembodiments, the composition includes dicyandiamide such as those soldby companies such as Alzchem Trostberg GmbH, Air Products and Chemicals,Inc., and Emerald Performance Materials LLC. The curing properties,e.g., curing speed of the material of the invention, are readilyadjustable by varying the type and the amount of curing agent, orcatalyst incorporated into the resin composition. In exemplaryembodiments, useful amounts of curing agent and/or catalyst aredetermined based on typical industrial 250-350° F. curing requirement,so that are compatible with industrial standard 250-350° F. resinsystems. By using the same concept in this invention, fast curesurfacing film was also achieved by selecting a curing agent andcatalyst, and by adjusting the concentration of the selected curingagent and catalyst in the formulation without sacrificing cure surfacequality.

In various embodiments, the resin composition includes a tougheningcomponent or agent. An exemplary toughening agent is a polymericmaterial(s) which can improve the material's fracture toughness andimpact resistance, to help prevent fracture or cracking of the curedfilm. The toughening agent can be liquid or solid. The liquid tougheningagent is preferably compatible with and mixable with or soluble in epoxyresins. The solid toughening agent is preferably compatible with anddispersible in epoxy resins. The toughening agent optionally containsvarious functional groups which can react with matrix resins of theresin composition. The toughening agent of use in this inventionincludes, but is not limited to, liquid or solid elastic materialshaving at least one reactive functional group in each molecule (prior toreacting). A suitable reactive functional group includes, but is notlimited to, a carboxylic group, a hydroxyl or phenolic group, an aminegroup, an anhydride group, an isocyanate group, acrylic groups, orcombinations of the same. The reactive functional groups react with thematrix resins to form an adduct to impart increased toughness andflexibility to the cured resin. In various embodiments, the tougheningagent is present in the total resin composition from about 2% to about20% by weight, e.g., from about 3% to about 15%, e.g., from about 4% toabout 10%. In various embodiments, the amount of toughening agent isfrom about 3% to about 15%, e.g., about 5% to about 15%, e.g., fromabout 4% to about 12%, e.g., from about 4% to about 10%, e.g., fromabout 8% to about 12%. In various embodiments, the functionalizedpolymer includes a toughening agent or acts as a toughening agent. In anexemplary embodiment, the matrix resin is one or more epoxy resin, suchas those sold by Dow Chemical Company, Momentive Performance Materials,Inc. (formerly Hexion Specialty Chemicals, Inc.), Huntsman InternationalLLC, and Emerald Performance Materials LLC., and the toughening agent isa carboxylic acid terminated liquid rubber, such as Hypro 1300X8 andHypro 1300X13, sold by Emerald Performance Materials LLC.

In various embodiments, the composition of the invention includes one ormore filler materials. The filler material includes one or more organicor inorganic fillers. Suitable fillers include, but are not limited to,those used in an adhesive, a sealant, a coating, and the like. Examplesof organic fillers include thermoplastic polymer powders made frompolyether ketone, polysulfone, and the like and thermoset polymerpowders made from cured rubber, acrylic resin, and the like. Examples ofinorganic fillers include silica (silicone dioxide), alumina, calciumcarbonate, aluminum trihydrate, titanium dioxide, and magnesiumhydroxide. Other suitable fillers include, but are not limited toalumina trihydrate powder such as those manufactured by Huber, and fumedsilica such as those sold by Evonik Industries. In various embodiments,the filler comprises from at least about 2% to not more than about 80%by weight of the total resin composition. In an exemplary embodiment,the filler content is from about 20% by weight to about 70% (by weightof the total resin composition). In various embodiments, the fillercontent is from about 25% to about 60% (by weight of the total resincomposition). In an exemplary embodiment, the filler is present in anamount of from about 50% to about 70%, e.g., from about 60% to about 70%(by weight of the total resin composition). In an exemplary embodiment,the filler is present in and amount from about 65% to about 70% (byweight of the total resin composition). An exemplary composition of theinvention includes filler at about 68.5% (by weight of the total resincomposition).

Exemplary fillers of use in the invention include silica, alumina,aluminum trihydrate, carbon black, titanium dioxide, antimony trioxideand zinc borate

The rheology of the materials of the invention is readily adjustable byvarying the amount of filler incorporated into the resin composition. Invarious embodiments, the filler mixture incorporates fumed silica. In anexemplary embodiment, the amount of silica filler is selected tooptimize flow control, and the amount present is from about 1% by weightto about 20% by weight of total resin composition, e.g., about 2% byweight to about 6% by weight of the total resin composition.

In various embodiments, the filler includes a mixture of fillers ofdifferent and distinct particle sizes. In the exemplary composition, thefillers include relatively small particles dimensioned to fill the voidsbetween larger particles and achieve higher filler loading while stillenabling good flow and fill. E.g., the fillers may include largerparticles with a mean particle size of about 5 to about 10 microns, andincreasingly smaller particles, e.g., those with a mean particle sizefrom about 5 nanometers to about 60 nanometers. The smaller particlesare added during preparation of the resin component until the requiredfiller loading is achieved. Use of different particle sizes may reducethe risk of too high viscosity and dryness. If the particle sizes arenot optimized, much of the resin fills the void volume betweenparticles. A mixture of different particle sizes improves wet out athigher filler loadings, because the void volume between larger particlesis partially filled with smaller particulates, making more of the resinavailable for flow and wetout. Thus, less of the resin is held in thevoid volume between particles and more of the filler is contacted orcoated with the resin. Use of the incorrect particle size distributionmay result in poor processability, dryness, lack of flow or otherundesirable characteristics.

The fillers can be synthesized with spherical morphology or milled orground from raw material into irregularly shaped particles. In variousembodiments, the use of a mixture of particle sizes and shapes ensures anesting of particles (i.e., smaller particles nesting in the gaps formedby the contact of the larger particles), which allows control of theamount of air or resin that is trapped in the voids between relativelylarger particles. The technique of the invention improves the flow andwetout of the resulting formulation. In various embodiments, the averageparticle size of the filler material is between about 5 nm and about 100micron. In various embodiments, the filler has an average particle sizegreater than about 5 nanometers. In various embodiments, the filler hasan average particle size less than about 100 micrometers.

In various embodiments, the filler is selected from aluminum trihydrate,fumed silica, TiO₂, carbon black, and a combination of the same. In anexemplary embodiment, the filler includes a solid material pre-dispersedor mixed in a liquid epoxy, that essentially remains solid through thecure cycle process of adhesive film melt and flow to cure in a compositepart matrix—(i.e., an engineering thermoplastic or thermoset fillerwhich remains solid can act as a filler).

In various embodiments, the “resin composition” is defined as the resiningredients, fillers, hardeners and catalysts ready to coat onto asubstrate. In an exemplary embodiment, the resin composition includes afiller comprising aluminum trihydrate. In various embodiments, thealuminum trihydrate has a mean particle size of about 4.7 micrometers.In an exemplary embodiment, the aluminum trihydrate has an averageequivalent diameter (d₅₀) of about 4.7 micrometers. In an exemplaryembodiment, the aluminum trihydrate has a d₉₀ of about 11.6 micrometers.In various embodiments, the filler includes fumed silica with a specificsurface area of from about 175 m²/g to about 225 m²/g, and a meanparticle size of about 12 micrometers. In various embodiments, thealuminum trihydrate filler is present at a percent by weight in thefinal resin/composition of about 1% to about 70% by weight, e.g., about1% to about 10% by weight.

In various embodiments, the filler comprises TiO₂ premixed in liquidepoxy. In various embodiments, the TiO₂ premixed in liquid epoxy has amean particle size of greater than about 100 nm. In various embodiments,the TiO₂ has a percent by weight in the final resin composition of about5% to about 70%.

In various embodiments, the filler comprises carbon black premixed inliquid epoxy. In an exemplary embodiment, the carbon black premixed inepoxy has a specific surface area of about 110 m²/g, and a mean particlesize of about 21 nm. In various embodiments, the carbon black is presentin a percent by weight in the final resulting resin/composition of about0.01% to about 10%, e.g., from about 0.1% to about 5%.

In various embodiments, the fillers include particles with a meanprimary particle size of about 1 micrometer to about 50 micrometers,e.g., from about 100 nanometers to about 800 nanometers, e.g., fromabout 10 nanometers to about 80 nanometers, or a combination of theseparticle size ranges. In various embodiments, the mean primary particlesize is less than or equal to about 100 micrometers, e.g., about 1micrometer to about 30 micrometers. In various embodiments, the maximumparticle size is less than or equal to about 60 micrometers.

In various embodiments, the filler comprises particles with a meanprimary particle size (numerical average particle size) of about 100 nmto about 50 micrometers, e.g., 20 nm to about 10 micrometers and amaximum particle size less than or equal to about 10 micrometers.Exemplary particles of use in the compositions of the invention are alsodescribed by reference to D₉₀ particle size (90% of the totalparticles). In various embodiments, the filler particles have a mean D₉₀particle size of less than or equal to about 10 micrometers. In variousembodiments, when D₉₀ is larger than 50 micrometers, it becomes moredifficult to control the film coating process, therefore, in variousembodiments, the D₉₀ particle size is less than about 50 micrometers.

In various embodiments, the filler comprises particles with a meanprimary particle size of about 5 nm to about 200 nm, e.g., about 10 nmto about 50 nm, and a maximum particle size less than or equal to about300 nm, e.g., less than or equal to about 100 nm. In variousembodiments, the resin composition has a percent by weight filler in thefinal resin composition of about 1% to about 10%.

In various embodiments, the filler comprises particles with a meanprimary particle size of about 1 micrometer to about 10 micrometers,e.g., about 1 micrometer to about 10 micrometers and a maximum particlesize less than or equal to about 30 micrometers, e.g., from about 1micrometer to about 10 micrometers. In various embodiments, thecomposition includes a percent by weight of filler in the final resincomposition of about 1% to about 20%.

In various embodiments, the filler comprises particles with a meanprimary particle size of about 5 nm to about 400 nm, e.g., about 10 nmto about 200 nm, and a maximum particle size less than or equal to about500 nm, e.g., less than or equal to about 300 nm. In variousembodiments, the composition includes filler at a percent by weight ofthe final resin composition of about 0.1% to about 5%.

In the embodiments discussed herein, various particle sizes anddistributions of readily available commercial fillers can be blended toprovide some packing density to allow higher use of filler without lossin wetout or loss of robustness in the melt's processability. Othercombinations will be apparent to those of skill in the art.

In various embodiments, the materials comprise one or more of the abovefillers. One will appreciate from the description herein that the fillermaterials may be provided in any number of combinations to achieve afiller loading and process and performance characteristics.

In various embodiments, the resin composition optionally includes, oneor more dispersant or coupling agent to enhance dispersion as well asimprove adhesion of the resin to the filler particles. Exemplarydispersants or coupling agents are surfactants which improve the abilityof the resin to wet the fillers. One or more dispersant can be added toreduce the viscosity while allowing relatively high filler loading. Inexemplary embodiments, the dispersant or coupling agent improves thechemical compatibility between the matrix resin and the filler surfaces.In exemplary embodiments, those dispersants containing chemicalfunctional groups which can react with epoxy resins or catalyze thecuring process should be avoided, as they may shorten the surfacing filmstorage life or work life. Suitable dispersants include, but are notlimited to, KenReact KR-38S sold by Kenrich Petrochemicals Inc, andDisperBYK-190 and DisperBYK-180, sold by BYK Chemie Gmbh.

In various embodiments, the resin composition includes one or moredefoamers (also called air release agent or antifoamer). Defoamers are asurfactant, which changes the surface tension of the liquid system tohelp resin ingredients wet the fillers as well as release any airbubbles entrapped during mixing and/or during cure to lower the porosityof the cured film. In various aspects, the “surfactants” are referred togenerally as a defoamer or air release agent. In various embodiments,the defoamer and/or air release agent is present in the range from about0.001% to about 5.0% by weight of the total resin composition, apreferred range is from about 0.005% to about 3% by weight of the totalresin composition, a more preferred range is from about 0.01% to about2.0% by weight of the total resin composition. Suitable defoamers orrelease agents include, but are not limited to, Foamkill products soldby companies such as Crucible Chemical Company, BYK 500 series productssold by BYK Chemie Gmbh, and antifoam products sold by Dow CorningCorporation.

In various embodiments, the resin composition includes one or morepigments. Many pigments are suitable for the resin composition based onthe color, opacity, particle size and dispersion ability requirement.Various colored compositions of the invention can be made, in somecases, transparent or black colored materials are desired, while inother cases, it may be desirable to use a colored material with goodopacity, rather than a transparent or black material to provideadditional protection against the reinforcement fiber becoming visibleduring sanding. In the case of sanding/repair, the evidence of a lack ofpigment aids the operator in making the decision to stop, eliminatingrisk of further fiber damage. A transparent surfacing film does not givea sanding operator any indication that the operator is sanding tooheavily and may be damaging fiber. Similarly, a black surfacing film maynot give a visual indicator for a black carbon fiber composite beingdamaged through sanding. In various embodiments, the pigment is otherthan transparent, can be black, aqua, red, light yellow, or acombination of the same, and preferably gray, but the pigment is notcounted in the resin formulation, we can add any color pigment asneeded. In various embodiments, less than 10% pigment is added whenneeded, while less than 5% pigment is preferred as it will notsignificantly alter the production process and the cured filmproperties.

In various embodiments, the composition includes one or more curingagent. Exemplary curing agents include one or more of an initiator, anaccelerator, and/or a catalyst. The curing agent may be selected fromchemical compounds that can be mixed or dispersed in a liquid or meltedin a resin system, at room temperature or high temperature such that nosignificant curing reaction of the resin composition will take placeduring the mixing. Exemplary curing agents undergo a further reactionwith resins at elevated temperatures to form the cured final filmproduct and impart mechanical strength and sandability. An example ofsuitable chemical compounds are amine-type curing agents which are oftenused to cure epoxy resins. One of skill in the chemical and materialarts will appreciate from the description herein that other chemicalcompounds may be selected and provided for this purpose. In variousembodiments, the total content by weight of the curing agent, initiator,catalyst, and/or accelerator in the resin composition is between about0.5% and about 30%. In an exemplary embodiment, the hardener is used ina range of about 2% to about 10% and the catalyst is used in a range ofabout 0.5% to about 15% by weight of the total resin composition

The resin composition is suitable for producing a supported orunsupported film suitable for curing in a composite matrix as a surfacethat provides cosmetic improvement and is suitable for painting aftercure in an otherwise conventional manner. The curing reaction may bebased on a polycondensation reaction, a poly-addition reaction, a freeradical reaction, or a cationic or anionic reaction. The curing reactionto convert the polymer/filler composition to a cured thermoset andfiller composite matrix may be performed with heat. During cure to athermoset, the functional groups generally react with hardeners with orwithout a of catalyst, initiator or accelerator to the point where thereaction of essentially >95% of the available reactive functional groupsoccurs and the resin no longer melts and flows, having been convertedfrom a b-stage mixture to a cured thermoset polymer. One skilled in theart can determine appropriate hardener and catalyst levels to derive aglass transition (Tg) that will approximate the reinforced fibercomposite matrix being covered with said surfacing film composition toenhance the surface cosmetics as referenced in this invention. Oneskilled in the arts can appreciate that the film form of the surfacingfilm can be formed and shaped to adapt to various contours of acomposite part. In an exemplary embodiment, the invention is a 250° F.to 350° F. curing epoxy mixture that cures to a Tg (by DSC, DMA, TMA) ofabout 100° C.-220° C. in 30-90 minutes. The curing reaction initiated inaccordance with the invention results in a cured film within areasonable period of time in the presence of curing agent, initiator,catalyst, accelerator or a combination of them. The resins can be eitherliquid or solid with different softening points. In various embodiments,the total resin content in the final product composition is betweenabout 30% and about 80% by weight compared to the supporting carrier. Inthe preferred embodiment, the resin composition undergoes apolycondensation reaction with amine hardener and urea catalyst orimidazole

One will appreciate that the resin composition and surfacing film mayinclude any number of the above materials in any combination dependingon the application and processing and performance characteristics.

The method of making the film composition and structure in accordancewith the present invention will now be described. In variousembodiments, the materials above are added in a particular sequence tomake sure good mixing, wetting, and dispersion occur. Mixing may becarried out from about room temperature to about 300° F. In general,heating may be used to reduce the system viscosity and improve wettingefficiency to the fillers. In various embodiments, the heatingtemperature and mixing time parameters are strictly controlled. One willappreciate that different heating temperatures and mixing times may berequired at different stages to achieve good mixing without triggering asignificant cure reaction or advancing. Generally, liquid epoxies arecombined, along with the toughener, lower molecular weight solid epoxiesare added, to melt and form the adduct. After the adduction step, highermolecular weight solid epoxy can be added, followed by the defoamer,powder fillers or pre-dispersed fillers prior to hardener and catalyst.In an exemplary embodiment, the higher molecular weight solid epoxycomponent is added after the adduction to provide more consistentbatch-to-batch viscosity results.

In exemplary embodiments, the product is not significantly subject tocure or advancement during the initial product formation phase where itis cast or extruded into a continuous supported film product form.Instead, the product is formulated to be stored for use by a customer,such as laying up the product or applying it to a mold with heat andpressure, to cure it into its final composite shape/purpose.

In exemplary embodiments, the invention provides a film designed toco-cure with various reinforcement fiber prepregs to form laminatecomposite parts. In various embodiments, these parts are formed from oneor more of carbon fiber, glass fiber, Aramid fiber, metal fiber, and/orother organic or inorganic fiber or hybrid fiber(s) and matrix resin.The laminate parts can be made using a unidirectional fiber prepreg withor without a special fiber orientation in the stack of plyconfiguration. The laminate parts can also be made by woven prepreg withvarious arrangements of fibers in the woven cloth. Final constructionsmay contain hollow core members such as honeycomb, thermoplastic orthermoset foam core or foam core in-situ formed by expandable filmadhesive or the like to provide body, strength, and stiffness to thehybrid construction containing a surfacing film exterior ply(s).

In various embodiments, the film is configured to be cured at atemperature from about 230° F. to about 350° F. The film may beconfigured to be compatible with typical industrial-standard 250° F. and350° F. curing materials. The cured film gives the laminate parts asmooth surface (i.e., no print-through or readout) with relatively fewsurface defects and minimal surface porosity. In an exemplaryembodiment, a surface with minimal surface porosity is a surface that ispaint-ready. In an exemplary embodiment, paint-ready refers to a surfacerequiring little or no reworking, repairing or sanding prior topainting. The film can be cured at a temperature and sufficient pressureor vacuum conditions to form a cured smooth surface which isporosity-free by visual inspection and sandable such that it is readyfor a paint preparation. The exemplary cured film is easily treated withor without a sanding process, or directly coated with or without aprimer coating without sanding prior to final coating. The curedsurfacing film of the invention is compatible with various coatingsbased on different chemistries such as typical epoxy, polyester, andpolyurethane coatings. An exemplary product cures under similarconditions as those products with which it is being combined.

In various embodiments, the mixed resin composition including the curingagent, initiator, catalyst, or accelerator is coated on supportingsubstrate which may be any of the following, though not limited to, awoven fabric or non-woven reinforcement such as a carrier/veil. Suitablecarriers or nonwoven veils can include, but are not limited to, a nylon,polyester, Aramid or other synthetic material, glass, carbon, metalcoated fibers, expanded metal mesh, polymeric mat, or thin wovenmaterial including, but not limited to, metal, glass, carbon and aramidfiber fabrics. The carrier may have an area weight equal to about 300g/m² or less.

In an exemplary process, the mixed resin composition can be applied tothe carrier by a film extrusion or metering roll process to form asupported film with even thickness. In other exemplary embodiments, aprocess such as reverse roll coating or another art-recognized processis utilized. A release liner is optionally applied on one side or bothsides of the formed film to protect the film. To extend the shelf lifeof the coated film, the film may be stored in a refrigerator (e.g., atabout 40° F. (4° C.)) or a freezer (e.g., below 0° F. (−18° C.)).

The composition of the invention is of significantly lower viscositythan existing products. Surfacing films with melt viscosities of fromabout 25 poise to about 200 poise, e.g., from about 50 poise to about150 poise, e.g., from about 75 poise to about 125 poise are exemplarysuitable surfacing films of the invention. Resins having these exemplaryviscocity provide improved control of resin mixing and forming of a thinfilm and controlling the film thickness without deterioration in otherperformance characteristics. The lowered viscosity also allows use ofthe resin composition in the composite manufacturing process without asolvent, which is typically necessary with ultra high viscosity resins.By eliminating the use of solvents, the composition and method of useavoids several problems present in solvent-based techniques such asunder-drying and the risk of increased tack and blistering from solventoutgassing during molding or paint cure with heat, over-drying, whichcan overstage the material, resulting in a loss of tack, loss ofdrapability leading to molding defects and structural weakness. Theinvention also avoids the use and disposal of volatile solvents.Accordingly, the invention provides a method of casting an epoxy resinwithout the use of a solvent as well as such cast resins and laid uparticles of manufacture incorporating such resins in either a cured ornon-cured state,

One will appreciate that the materials and methods of the inventionallow for use of a wide range of materials in a hot melt manufacturingprocess. The invention provides a thermosetting resin in a relativelylow viscosity range amenable to hot melt processing without theprocessing limitations of existing materials. The thermosetting resinresults in a good performing film. The film of the invention has a longout time (e.g., more than 3 weeks) at room temperature, (roomtemperature out time defined as retaining its drapeability and tack overtime) thus enabling its use for large scale structures which can takemany days to lay up, and the cured surface is sandable with lowporosity, which makes the surface easier to paint. The resin compositionand resulting surfacing film of the invention also provides more robustpost-processing such as painting or sealing coats—cosmetic or functionalcoatings to seal out weather, moisture, UV damage, etc.—in addition topainting for visual appeal such as logos and color scheme.

Suitable support carriers or reinforcement include, but are not limitedto, woven and non-woven carriers comprising polyester fiber, nylonfiber, glass fiber, aramid fiber, carbon fiber, and combinations of thesame. In this product, the support or carrier is not a separate film(i.e., release carrier) but an integrated support framework of fibers,either polymer or inorganic, random or woven to provide stability in thefilm matrix while handling large sheets, placing and laying up on largesupport structures and the like. Exemplary carriers include those soldby Technical Fiber Products, Inc., Precision Fabrics Group, and CerexAdvanced Fabrics, Inc. In an exemplary embodiment, a low weightpolyester veil over glass or other mineral sheets which contain higherdensity fibers is utilized.

EXAMPLES

The invention is further illustrated by the Examples that follow. TheExamples are not intended to define or limit the scope of the invention.

Example 1

Several reactant resin mixtures for forming surfacing films with goodopacity were prepared with the following component contents:

-   -   1. A liquid epoxy resin or a mixture of liquid epoxy resins        selected from low viscosity liquid epoxy resins, about 5 to 60%        in weight;    -   2. One or more solid bisphenol A based epoxy resin which has a        softening point range from 50° C. to 130° C., about 2% to 40% in        weight;    -   3. Solid epoxy phenol novolac, epoxy cresol novolac or other        multifunctional epoxy resin with a functionality of about 2.2 or        more, about 1-30% by weight;    -   4. Carboxylic functionalized butadiene-acrylonitrile copolymer        with average functionality of about 2 or more than 2, 1-20% by        weight;    -   5. Defoamer or air release agent: about 0.001% to about 5%;    -   6. One, two or three fillers and pigments selected from silica,        aluminum hydroxide, alumina, carbon black, titanium dioxide,        calcium carbonate, average particle size from 5 nm to 100        micron, preferably range of the weight percentage is from about        20% to 60%, with or without organic surface treatment;    -   7. Curing agent dicyandiamide (Dicy) from about 2% to about 10%;        and    -   8. Accelerator or catalyst selected from urea, substituted urea,        imidazole, modified imidazole, tertiary amine: from about 0.5%        to about 5%.

Optimizing Filler Packing Density Filler Amount Filler Size Range #1  ~1to 35% 5 to 50 nm (0.005-0.05 microns) #2 ~25 to 70% 100-800 nm (0.1 to0.8 microns) #3 ~5-35% 1,000 to 40,000 nm (1 to 40 microns)

A comparison of the films with high, medium and low viscosities issummarized in the following table

TABLE 1 Viscosity Thin film Cured film^((b)) at 160° F. Hot meltthickness Porosity or Trace Exper. (71° C.) mixing Coating control andCoated pinhole of No. Pa · s ability film adjustability film Appear.free^((c)) Sand ability streaks 1 66^((a)) Difficult Poor DifficultUneven — — — — 2 59^((a)) Difficult OK Difficult Uneven Smooth Yes YesYes 3 46 Good Good Good Very Smooth Yes Good No uniform 4 37 Good GoodGood Very Smooth Yes Good No uniform ^((a))Viscosity difficult tohandle: can not get good wetting and dispersion of the fillers andpigments ^((b))10 plys of typical commercial carbon fiber unidirectionalprepreg, one ply surfacing film on top, standard layup and vacuumbagging procedure and cured in auto clave 90 min at 275° F. (135° C.) at40 psi ^((c))Visual inspection

Competitive Example

An epoxy based competitive product is analyzed and summarized in thetable below.

TABLE 2 Cured film^((e)) Viscosity Thin film Porosity at 160° F. Hotmelt thickness or Trace Experiment (71° C.) mixing Coating control andCoated pinhole Sand of No Pa · s ability film adjustability filmAppearance free ability streaks 5 Over the Un Must OK with OK Smooth YesGood No limit^((d)) processable have to solvent with by hot melt usesolvent solvent (a) The viscosity was over the limit of the rheometer,which means the viscosity is at least 15 times higher than that ofExperiment 1 (b) Same condition as (b), i.e., 10 plies of typicalcommercial carbon fiber unidirectional prepreg, one ply surfacing filmon top, standard layup and vacuum bagging process and cured in autoclave 90 min at 275° F. (135° C.) at 40 psi

The resin mixture and surfacing film were generally prepared using thefollowing process. First, components (1) through (4) were mixed andreacted at about 240° F. to about 290° F. for about 1 hour to about 10hours to make an in-situ adduct. The adducting process was found toapproximately double the viscosity of the mixture.

Next, components (5) and (6) were added to the mixture. The mixture washeated and mixed until it became essentially homogeneous. Although thefillers and pigments were added separately (i.e., step-by-step insequences), it is possible to add all of the fillers and pigments at onetime to the mixture. Pre-dispersed/mixed fillers and pigments withresins may also be used. It may be desirable to ensure proper mixingsuch that the fillers and pigment are well wetted and homogeneouslydispersed to improve performance of the final film.

Next, component (7) was added to the reactant mixture at temperatures atwhich the system (mixture) was relatively easy to mix without triggeringsignificant curing or advancing, which is would be understood by one ofskill in the chemical and material arts.

After mixing the curing agent into the system, an accelerator orcatalyst was optionally added. Similar to the curing agent, theaccelerator or catalyst is added at a sufficient temperature to improvemixing without triggering significant curing or advancing.

The resin composition (reactant mixture) was immediately used to make asurfacing film after preparation. The surfacing film was coated on anon-woven carrier by a calendaring/metering process to form a supportedcomposite film with essentially even and uniform thickness. A releaseliner was applied on one side or both sides of the formed film toprotect the film. After metering/coating the material is cooled to roomtemperature, thereby maintaining coating and preventing advancement. Thecoated film was then sealed, packaged, and stored at 0° F. (−18° C.) forsubsequent cure and use in making composite parts.

Based on the above process, several compositions were formed. Theproduct properties were measured and are reported in Table 1.Comparative examples are shown in Table 2.

With reference to Table 1, four resin compositions with relatively high,medium and low viscosities were made by adjusting the ratios of adduct,liquid and solid resins, and the fillers. To compare the processabilityof each, the viscosities of the resins were measured by a rheometer at160° F. (71° C.). The viscosity was in the range of about 30 Pa·s toabout 70 Pa·s. It was determined that a viscosity above 100 Pa·s wouldbe difficult to control and use to make a film with satisfactorycharacteristics under typical hotmelt manufacturing coating conditions.

Formulations 1 and 2 were difficult to mix due to high viscosity. Thefillers were not fully wetted and clumps of dry particles were observedin the mix. The film could be coated with formulation 2 and the surfacewas smooth and porosity free, but the cured film showed unevendistribution of the fillers. The films coated with formulations 3 and 4had good tackiness and were relatively easy to handle/work during layup.The films had more than three weeks out time, i.e., they still had goodtackiness after three weeks of exposure to ambient temperature. The filmwas curable at 250° F./350° F. (121° C., 177° C.). The film was appliedto the outside surface of a laminate and co-cured with a compositeprepreg of like cure conditions to become part of a final laminatestructure. After cure, formulations 3 and 4 provided good aestheticswith porosity free surfaces. The cured surfaces have low surfaceroughness and line free. The cured film surfaces were easy to sand.

Example 2

Several reactant resin mixtures for forming surfacing films withsemi-transparent or black color were prepared with the followingcomponents:

-   -   1. A liquid epoxy resin or a mixture of liquid epoxy resins        selected from low viscosity liquid epoxy resins, about 5 to 60%        in weight;    -   2. One or more solid bisphenol A based epoxy resin which has a        softening point range from 50° C. to 130° C., about 2% to 40% in        weight;    -   3. Solid epoxy phenol novolac, epoxy cresol novolac or other        multifunctional epoxy resin with a functionality of about 2.2 or        more, about 1-30% by weight;    -   4. Carboxylic functionalized butadiene-acrylonitrile copolymer        with average functionality about 2 or more than 2, 1-20% by        weight;    -   5. A defoamer/air release agent selected from Foamkill products        sold by Crucible Chemical Company, BYK 500 series products sold        by BYK Chemie Gmbh, and antifoam products sold by Dow Corning        Corporation: about 0.001% to about 5%;    -   6. One, two or three fillers and pigments selected from,        alumina, aluminum hydroxide, magnesium oxide, zinc borate,        zinc-magnesium complex, zinc stannate based compound, antimonite        trioxide, carbon black, yellow pigment, red pigment, and calcium        carbonate or a combination thereof, average particle size from 5        nm to 100 micron, preferably range of the weight percentage is        from about 20% to 60%, with or without organic surface        treatment;    -   7. Curing agent dicyandiamide (Dicy) from about 2% to about 10%;        and    -   8. Accelerator or catalyst selected from urea, substituted urea,        imidazole, modified imidazole, tertiary amine: from about 0.5%        to about 5%.

TABLE 3 Cured film^((c)) Thixotrpoic Hot Thin film Porosity index atmelt thickness or Exper. 160° F. mixing Coating control and Coatedpinhole Sand Trace of No. (71° C.) ability film adjustability filmAppear. free^((d)) ability streaks 6 High Poor OK Difficult^((a))Uniform Smooth Yes Good No 7 High Poor OK Difficult^((a)) Uniform SmoothYes Good No 8 Medium Good Good Good^((b)) Very Smooth Yes Good Nouniform 9 Low Good Good Good^((b)) Very Smooth Yes Good No uniform^((a))Difficult to mix and difficult to coat thin film and control thethin film thickness; ^((b))Easy to mix and easy to control the thin filmthickness, the film areal weight can be as low as 0.010 psf (lbs/ft²)(50 g/m²); ^((c))10 plys of typical commercial carbon fiberunidirectional prepreg, one ply surfacing film on top, standard layupand vacuum bagging procedure and cured in auto clave 90 min at 275° F.(135° C.) at 40 psi; ^((d))By visual inspection

The resin mixture and surfacing film were generally prepared using thefollowing process. First, components (1) through (4) were mixed andreacted at about 240° F. to about 290° F. for about 1 hour to about 10hours to make an in-situ adduct. The adducting process was found toapproximately double the viscosity of the mixture.

Next, components (5) and (6) were added to the mixture. The mixture washeated and mixed until it became essentially homogeneous. Although thefillers and pigments were added separately (i.e., step-by-step insequences), it is possible to add all of the fillers and pigments at onetime to the mixture. Pre-dispersed/mixed fillers and pigments withresins may also be used. It may be desirable to ensure proper mixingsuch that the fillers and pigment are well wetted and homogeneouslydispersed to improve performance of the final film.

Next, component (7) was added to the reactant mixture at temperatures atwhich the system (mixture) was relatively easy to mix without triggeringsignificant curing or advancing, which is would be understood by one ofskill in the chemical and material arts.

After mixing the curing agent into the system, an accelerator orcatalyst was optionally added. Accelerator or catalyst is selected fromurea, substituted urea, imidazole, modified imidazole or tertiary amine.Similar to the curing agent, the accelerator or catalyst is added at asufficient temperature to improve mixing without triggering significantcuring or advancing.

The resin composition (reactant mixture) was immediately used to make asurfacing film after preparation. The surfacing film was coated on anon-woven carrier by a calendaring/metering process to form a supportedcomposite film with essentially even and uniform thickness. A releaseliner was applied on one side or both sides of the formed film toprotect the film. After metering/coating the material is cooled to roomtemperature, thereby maintaining the coating and preventing advancement.The coated film was then sealed, packaged, and stored at 0° F. (−18° C.)for subsequent cure and use in making composite parts.

Based on the above process, several compositions were formed. Theproduct properties were measured and are reported in Table 3.

With reference to Table 3, four resin compositions with relatively high,medium and low Thixtropic Index were made by adjusting the ratios ofadduct, liquid and solid resins, and the fillers. To compare theprocessability of each, the Thixtropic Index of the resins were measuredby a rheometer at 160° F. (71° C.). It was determined that a highThixotropic Index would be difficult to control and use to make a filmwith satisfactory characteristics under typical hotmelt manufacturingcoating conditions.

Formulations 6 and 7 were difficult to mix due to high Thixtropic Index.The fillers were not fully wetted and clumps of dry particles wereobserved in the mix. The film could be coated with formulation 6 and 7and the surface was smooth and porosity free, but the cured film showeduneven distribution of the fillers and difficult to make thin film.Formulations 8 and 9 were easy to handle, the film thicknesses (arealweight) were easy to control, within the film thickness range from ashigh as 0.150 psf (lbs/sf²) or 730 g/m²to as low as 0.010 psf (lbs/sf²)or 50 g/m². The films coated with formulations 8 and 9 had goodtackiness and were relatively easy to handle/work during layup. Thickerfilms are preferred due to the easy handling and higher productivity.The films had more than three weeks out time, i.e., they still had goodtackiness after three weeks of exposure to ambient temperature. The filmwas 250° F./350° F. (121° C./177° C.) curable. The film could be appliedon the outside surface of a laminate and co-cured with a compositeprepreg of like cure conditions to become part of a final laminatestructure. After cure, formulations 8 and 9 provided good aestheticswith semi-transparent or black color and porosity free surfaces. Thecured surfaces on various composite parts with different cure methodshave shown low roughness and mirror like surfaces. The cured filmsurfaces were easy to sand. In a sanding test, the cured 0.150 psf(lbs/sf²) or 730 g/m² surfacing film on a carbon fiber laminate wereeasily able to completely sand down to the carbon layer. With a slightlysanding, the formulations 8 and 9 showed good compatibility and adhesionwith a commercial industrial coating which is widely used in compositepainting.

Example 3

This material was prepared in a manner similar to that of Example 2,

-   -   1. The mixed resin was partially replaced by a brominated epoxy        resin by about 20% to about 50%;    -   2. Defoamer or air release agent selected from Foamkill products        sold by companies such as Crucible Chemical Company, BYK 500        series products sold by BYK Chemie Gmbh, and antifoam products        sold by Dow Corning Corporation: about 0.001% to about 5%;    -   3. One, two or three fillers and pigments selected from,        alumina, aluminum hydroxide, magnesium oxide, zinc borate,        zinc-magnesium complex, zinc stannate based compound, antimonite        trioxide, carbon black, yellow pigment, red pigment, and calcium        carbonate or a combination thereof, average particle size from 5        nm to 100 micron, preferably range of the weight percentage is        from about 20% to 60%, with or without organic surface        treatment;    -   4. Curing agent dicyandiamide (Dicy) from about 2% to about 10%;        and    -   5. One or two accelerator or catalyst selected from urea,        substituted urea, imidazole, modified imidazole, tertiary amine:        from about 0.5% to about 5%.

The same resin mixing procedure and film coating process used inExamples 1 and 2 were employed in Example 3. The resin composition(reactant mixture) was immediately used to make a surfacing film afterpreparation. The surfacing film was coated on a woven or a non wovenglass carrier by a calendaring/metering process to form a supportedcomposite film with essentially even and uniform thickness. A releaseliner was applied on one side or both sides of the formed film toprotect the film. After metering/coating the material is cooled to roomtemperature, thereby maintaining coating and preventing advancement. Thecoated film was then sealed, packaged, and stored at 0° F. (−18° C.) forsubsequent cure and use in making composite parts.

Based on the above process, several compositions were formed. Theproduct properties were measured and are reported in Table 4.

TABLE 4 Hot Thin film The melt thickness laminate Cured film^((b))Exper. Contains mixing Coating control and passes Coated Porosity orSand Trace of No defoamer ability film adjustability FST test(a) filmAppear. pinhole free^((c)) ability streaks 10 No Good OK Good YesUniform Smooth OK Good No 11 Yes Good OK Good Yes Uniform SmoothExcellent^((d)) Good No (a)FST: flammability and smoke density testincluding the following tests FAR 25.853 Appendix F, Part I (a)(1)(i)and (a)(2)(iii) FAR 25.853 Appendix F, Part IV (OSU Heat Release Rate)FAR 25.853 Appendix F, Part IV (OSU Heat Release Rate) ^((b))Thelaminates were made by using typical Newport Adhesives and Composites'special flame retardant carbon fiber unidirectional prepreg (pleaserefer to Newport 4030 Product Datasheet), with one ply flame retardantsurfacing film on top, standard layup and vacuum bagging procedure andcured in auto clave 90 min at 275° F. (135° C.) at 40 psi ^((c))Byvisual inspection

With reference to Table 4, two resin compositions with and withoutdefoamer (Formulations 10 and 11) were made by adjusting the ratios ofbrominated epoxy resin content, and the flame retardant content. It wasdetermined that a defoamer/air release agent is needed to provide a filmwith satisfactory characteristics under typical hotmelt manufacturingcoating conditions.

Formulations 10 and 11 were easy to mix. The film thickness (wt/area)was easy to control, within the film thickness range from as high as0.150 psf (lbs/sf²) or 730 g/m² to as low as 0.010 psf (lbs/sf²) or 50g/m². The films made from formulations 10 and 11 had good tackiness andwere relatively easy to handle/work during layup. Films thicker than 20psf (lbs/sf²) are of particular utility due to the easy handling andhigher productivity. The films were still fully functional after morethan three weeks out time, i.e., they still had good tackiness afterthree weeks of exposure to ambient temperature. The film was curable at250° F./350° F. (121° C./177° C.). The film could be applied to theoutside surface of a laminate and co-cured with a composite prepregcurable under similar conditions to become part of a final laminatestructure. After cure, formulations 10 and 11 provided good aestheticswith semi-transparent or black color and porosity free surfaces whileformulation 11 showed better leveling property than formulation 10. Thecured surfaces on various composite parts with different cure methodshave shown low roughness without fiber print through. The cured filmsurfaces were easy to sand. With a slight sanding, the formulations 10and 11 showed good compatibility and adhesion with a commercialindustrial coating which is widely used in composite painting. Thesurfacing film co-cured with Newport Adhesives and Composites, Inc.'sspecial flame retardant prepregs pass the FST test (FAR flammability andsmoke density test, i.e., FAR 25.853 Appendix F, Part I (a)(1)(i) and(a)(2)(iii), FAR 25.853 Appendix F, Part IV (OSU Heat Release Rate), andFAR 25.853 Appendix F, Part IV (OSU Heat Release Rate)).

Example 4

To make a fast cure surfacing film, the method of Example 1, steps 7 and8, was utilized with one or two curing agent(s) and accelerator(s)selected from urea, substituted urea, imidazole, substituted imidazole,amine, substituted amine, tertiary amine in an amount of from about 5%to about 30%.

TABLE 5 Cured film^((e)) Hot Thin film Differences in PorosityPercentage melt thickness DSC Onset and or Trace Exper. of curing mixingCoating control and Coated Peak pinhole Sand of No agent(s)^((a))ability film adjustability film temperatures Appear. free^((c)) abilitystreaks 12  8%^((b)) Good OK Good Uniform 125° C.^((c)) Tacky Yes^((d))Good No 143° C.^((d)) 13 10%^((b)) Good OK Good Uniform 120° C. SmoothYes^((d)) Good No 138° C. Tacky free ^((a))The concentration of thecuring agent(s) is the total amount of the curing agent and acceleratorselected from the group of the materials described in paragraph 83.^((b))Percentage of the curing agent by weight of the total resincomposition. ^((c))DSC onset temperature for the mixed resin offormulation 12 was measured by a Perkin Elmer Diamond DSC. ^((d))DSCpeak temperature for the mixed resin of formulation 12 was measured by aPerkin Elmer Diamond DSC. ^((e))10 plys of typical commercial carbonfiber unidirectional prepreg, one ply surfacing film on top. Thematerial was cured with preheated hot press, 6 minutes at 300° F.,hot-in hot-out with 40 psi pressure.

The same resin mixing procedure and film coating process used inExamples 1 and 2 were employed in Example 4. The resin composition(reactant mixture) was immediately used to make a surfacing film afterpreparation. The resin composition was coated on a woven or a non wovenglass carrier by a calendaring/metering process to form a supportedcomposite film with essentially even and uniform thickness. A releaseliner was applied on one side or both sides of the formed film toprotect the film. After metering/coating the material is cooled to roomtemperature, thereby maintaining coating and preventing advancement. Thecoated film was then sealed, packaged, and stored at 0° F. (−18° C.) forsubsequent cure and use in making composite parts.

Based on the process described above, several compositions were formed.The product properties were measured and are reported in Table 5.

With reference to Table 5, two resin compositions with relatively lowand high curing speed were made by adjusting the ratios of resins andthe curing agent/catalyst. The DSC onset and peak temperatures measuredby a Perkin Elmer Diamond DSC with 10° C./min ramping rate were employedas indicators to compare the curing speed. It was determined that DSConset and peak temperature could be used as an indicator for fast curecapability, and lower DSC onset and peak temperatures would give fastercure performance.

Formulations 12 and 13 were easy to handle, the film thicknesses (arealweight) were easy to control, within a film thickness range from as highas 0.150 psf (lbs/sf²) or 730 g/m² to as low as 0.020 psf (lbs/sf²) or50 g/m². The films coated with formulations 12 and 13 had good tackinessand were relatively easy to handle/work during layup. Thicker films arepreferred due to the easier handling and higher productivity. The filmsstill had useful characteristics after more than two weeks out time,i.e., they still had good tackiness after three weeks of exposure toambient temperature. The films were 250° F./350° F. (121° C./177° C.)curable with fast cure capability. The film could be applied on theoutside surface of a laminate and co-cured with a composite prepreg oflike cure conditions to become part of a final laminate structure. Aftercure, formulations 12 and 13 provided good aesthetics withsemi-transparent or black color and porosity free surfaces. The curedsurfaces on various composite parts with different cure methods haveshown low roughness smooth surfaces without the fiber print-through. Thecured film surfaces were easy to sand. With a slight sanding, theformulations 12 and 13 showed good compatibility and adhesion with acommercial industrial coating which is widely used in compositepainting. In a fast cure test using two laminate panels, one was coveredduring layup with formulation 12 surfacing film, the other was coveredduring layup with formulation 13 surfacing film. Both samples were curedfor 5˜6 minutes with a pre-heated hot press at 300° F., in a hot-inhot-out process. Formulation 13 was well cured with excellent surfacequality and the cured surface was completely tack free, whileformulation 12 provided the same surface appearance but with a littletack, which means formulation 12 could not be fully cured within 5˜6minutes range at this temperature, suggesting that higher curing agentcontent is needed.

The foregoing descriptions of specific embodiments of the presentinvention have been presented for purposes of illustration anddescription. They are not intended to be exhaustive or to limit theinvention to the precise forms disclosed, and obviously manymodifications and variations are possible in light of the aboveteaching. The embodiments were chosen and described in order to bestexplain the principles of the invention and its practical application,to thereby enable others skilled in the art to best utilize theinvention and various embodiments with various modifications as aresuited to the particular use contemplated. It is intended that the scopeof the invention be defined by the Claims appended hereto and theirequivalents.

1.-12. (canceled)
 13. A resin composition for forming a thermosettingsurfacing film, the composition comprising: a resin component comprisingone or more epoxy resins selected from a liquid resin, a solid resin, asemi-solid resin and a combination thereof; from about 1% to about 20%(by weight of the total composition) of a carboxylic acid functionalizedpolymer having an average functionality of about 2 or more carboxylicacids prior to reacting said polymer with said resin component; fromabout 25% to about 60% (by weight of the total composition), with orwithout an organic surface treatment, of at least one filler materialwith a D90 particle size of between 1 and 30 microns, said resincomposition having a viscosity of less than about 100 Pa·s at 71° C.,and being free of solvent.
 14. The composition of claim 13, wherein theone or more epoxy resins comprises: (A) from about 5% to about 60% (byweight of the total composition) of a resin fraction selected from a lowviscosity liquid epoxy resin, and a combination of said low viscosityliquid epoxy resin with one or more resin selected from a solid resin,and a semi-solid; and (B) from about 2% to about 40% (by weight of thetotal composition) of one or more solid bis-phenol A based epoxy resinshaving a softening point range from about 50° C. to about 130° C. 15.The composition of claim 13, further comprising: (D) from about 0.001%to about 5% (by weight of the total composition) of a defoamer and/orair release agent.
 16. The composition of claim 13, further comprising:(F) from about 2% to about 10% (by weight of the total composition) of acuring agent.
 17. The composition of claim 13, further comprising: (G)from about 0.5% to about 5% (by weight of the total composition) of anaccelerator or catalyst selected from a urea, a substituted urea, animidazole, a substituted imidazole, a tertiary amine and a combinationthereof.
 18. The resin composition according to claim 13, wherein the atleast one filler has D90 particle size of less than 10 microns.
 19. Theresin composition of claim 13, wherein the composition has a viscosityfrom about 20 Pa·s to about 100 Pa·s at 71° C.
 20. The resin compositionof claim 13, wherein the filler material comprises is about 50% of thetotal composition(by weight).
 21. The resin composition of claim 13,wherein the at least one filler is aluminum trihydrate.
 22. Asolvent-free surfacing resin composition which is prepared by: (A)reacting, (1) from about 5% to about 60% (by weight of the totalcomposition) of a resin fraction selected from a low viscosity liquidepoxy resin and a combination of said low viscosity liquid epoxy resin,with one or more resin selected from a solid resin, and a semi-solidresin; (2) from about 2% to about 40% (by weight of the totalcomposition) of one or more solid bis-phenol A based epoxy resins havinga softening point range from about 50° C. to about 130° C.; (3) fromabout 1% to about 20% (by weight of the total composition) of acarboxylic acid functionalized polymer; thereby forming an adduct; and(B) mixing with said adduct, (1) from about 0.001% to about 5% (byweight of the total composition) of a defoamer and/or air release agent;and (2) from about 25% to about 60% (by weight of the totalcomposition), with or without an organic surface treatment, of at leastone filler material having a D90 particle size of between 1 and 30microns and optionally one or more pigments, (3) from about 2% to about10% (by weight of the total composition) of a curing agent; and (4) fromabout 0.5% to about 5% (by weight of the total composition) of anaccelerator or catalyst selected from a urea, a substituted urea, animidazole, a substituted imidazole, a tertiary amine and a combinationthereof, thereby forming said resin composition.
 23. A solvent-free filmproduct formed from the surfacing resin composition of claim 22, saidproduct formed by a method comprising: (i) applying or coating thesurfacing resin to a carrier to form a film product; and (ii) after theapplying, cooling the film product.
 24. The solvent-free surfacing resincomposition of claim 22, wherein the carboxylic acid functionalizedpolymer has an average functionality of equal to or greater than about2.
 25. The solvent-free surfacing resin composition of claim 22, whereinthe carboxylic acid functionalized polymer is a di-carboxylic acidfunctionalized polymer.
 26. The solvent-free surfacing resin compositionof claim 22, wherein the composition has a viscosity from about 20 Pa·sto about 100 Pa·s at 71° C.